EntitySlime.java

public boolean getCanSpawnHere() {
    Chunk var1 = this.worldObj.getChunkFromBlockCoords(new BlockPos(MathHelper.floor_double(this.posX), 0, MathHelper.floor_double(this.posZ)));
    if (this.worldObj.getWorldInfo().getTerrainType() == WorldType.FLAT && this.rand.nextInt(4) != 1)
        return false;
    else {
        if (this.worldObj.getDifficulty() != EnumDifficulty.PEACEFUL) {
            BiomeGenBase var2 = this.worldObj.getBiomeGenForCoords(new BlockPos(MathHelper.floor_double(this.posX), 0, MathHelper.floor_double(this.posZ)));
            if (var2 == BiomeGenBase.swampland && this.posY > 50.0D && this.posY < 70.0D && this.rand.nextFloat() < 0.5F && this.rand.nextFloat() < this.worldObj.getCurrentMoonPhaseFactor() && this.worldObj.getLightFromNeighbors(new BlockPos(this)) <= this.rand.nextInt(8))
                return super.getCanSpawnHere();
            if (this.rand.nextInt(10) == 0 && var1.getRandomWithSeed(987234911L).nextInt(10) == 0 && this.posY < 40.0D)
                return super.getCanSpawnHere();
        }
        return false;
    }
}